Switch to case insensitive search in DataTables?

[LTLA]

Save users the trouble of matching the case, e.g., for human vs mouse or whatever. This should be orthogonal to the regex. Shouldn't break too many existing applications - anyone restoring sessions with an old string may suddenly get a few more hits if they were relying on case, but most of these situations can be remedied by slapping a ^Xxxx to match the start of the string.

filterDTColumn will have to be updated to set ignore.case=TRUE in any grepl() statements.

[kevinrue]

Consider adding a checkbox to toggle on/off